The problem is that attacker can modify ping's output without having direct access to this program. Example:

ilya@juil:~$ ping www.aha.ru
PING distributed.zenon.net (195.2.91.103): 56 data bytes
     ^^^^^^^^^^^^^^^^^^^^^
64 bytes from 195.2.91.103: icmp_seq=0 ttl=120 time=69.3 ms
64 bytes from 195.2.91.103: icmp_seq=1 ttl=120 time=64.6 ms

[download]

Note that ping (at least its version on my Linux desktop) queries DNS to find canonic name of pinged host. Since attacker controls networking address of pinged computer and may potentialy control corresponding DNS server he can control this part of ping's output. In general if you use output of any networking program you must be extra careful about it. There are many ways how attacker can tamper it without having direct access to your computer.

--
Ilya Martynov, ilya@iponweb.net
CTO IPonWEB (UK) Ltd
Quality Perl Programming and Unix Support UK managed @ offshore prices - http://www.iponweb.net
Personal website - http://martynov.org

In reply to Re: Re: Re: Re: Ping from HTML by IlyaM
in thread Ping from HTML by fouttyw

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.